In magnetic resonance imaging apparatuses, it is important to realize magnetization distribution homogeneity to obtain MR images without an imbalance in sensitivity. However, there is a case where nonuniformity occurs in a spatial distribution of the high frequency magnetic field, i.e., a sensitivity map (hereinafter referred to as a “B1 sensitivity map”) of a radio frequency (RF) coil due to influence of a measurement target and a coil, which causes magnetic field inhomogeneity.
In order to mitigate inhomogeneity of the magnetic field, the amplitudes and the phases of the RF phases are properly controlled, and a strength distribution (hereinafter referred to as a “B1 map design value”) is applied onto the B1 sensitivity map. If the RF pulses are properly controlled so that the B1 map design values exhibit the inverse characteristics of the B1 sensitivity map, the magnetization distribution obtained by the products of B1 map design values and the B1 sensitivity map becomes uniform.
The B1 map design values are calculated by a method based on a linear approximation such as a small tip angle (STA) approximation, for example. The inhomogeneity of the high frequency magnetic field B1 varies depending on a subject or a part of a subject to be measured. Accordingly, when planning design guidelines for RF pulses to be applied by using the STA approximation, an optimal design method is needed depending on the subject to be imaged.